Optical fibres are being used in a wide variety of applications. The majority of these applications employ the optical fibres for their light transmitting properties. It is known that coherent optical radiation from a laser source can be transmitted along a suitable optical fibre for many hundreds of kilometers.
In contrast to the transmission properties, optical fibres have also been used for their loss properties. One example is U.S. Pat. No. 4,830,461 assigned to Bridgestone Corporation. This patent describes a pressure sensor made from an optical fibre with a light emitting means at one end and a light receiving means at the other end. When pressure is applied to the fibre a deformation occurs which causes transmission loss which is detected by the light receiving means. The applied pressure can be calculated from the measured decrease in signal.
Another field of use of optical fibres is in novelty applications. In our co-pending published international application number WO 02/095289 we describe a side-scattering light guide that has a range of uses including decorative lighting, advertising and illuminated clothing. This last application has proven to be of particular interest, but presents a number of difficulties that have heretofore not been addressed. In particular, light guides for use in clothing, such as illuminated shoe laces, must be very flexible but maintain reasonable light transmission properties for up to a meter.
Suitable light guides have not been produced. The existing light guides are either too brittle for the application or too lossy when bent to a desired configuration.